CO2 Promotes Ground Cover Via Transpiration Water Loss Reductions

CO2 Promotes Ground Cover Via Transpiration Water Loss Reductions

Grasslands are greening due to high CO2 helping plants to conserve water.

Startling research just published in the Journal Nature provides clear data showing the coupling of high CO2 with plants observed reduction in transpiration water loss. The report using sophisticated isotope techniques shows that moisture in the air is overwhelming due to plant transpiration as compared to evaporation. Plants put 4-5 times more water into the air than evaporation!

This is especially important in the most sensitive and responsive ecosystem on earth, that region known as “drylands.” Drylands are vegetated mostly with grasses, you know what grass is right, it’s that plant life that is green and lush in the wet times and brown and dusty in the dry times.

Suguaro_rain transpiration to comeWhen there is water in a dryland ecosystem the grasses are lush and growing and we call that condition “good ground cover.” That good ground cover protects the soil from blowing in the wind. If it weren’t for the fact that downwind another ecosystem hadn’t evolved awaiting that dust in the wind, the more grass and ground cover the better.

Tragically that is not the case and in fact the largest and most vital ecosystem on this blue planet is downwind waiting for its dust, that ecosystem is what we call ocean pastures.

So the fact that land plants which must obtain CO2 across wet membranes that facilitate gas exchange, just like you and I. Are reducing the time that gas exchange takes place as high and rising CO2 concentration in the air gives them an energy benefit shouldn’t come as a surprise. We have seen the evidence of this happening. What we didn’t have until now were some great numbers on just how potent CO2 is in this water conservation role.

It takes a lot of energy and water for plants to perform gas exchange. With the 40+% more Co2 in the air today and its rising rapidly plants are saving energy and and lot of water.

As the Scott Jasechko paper in Nature shows 60% of atmospheric water normally comes from the plants. Indeed this is the norm for atmospheric water everywhere.

stomate1In the present atmosphere where there has been a 40+% increase in CO2, the corresponding conservation of the energy and water that benefits plants by allowing them to do less transpiration is in the range of 10% – 20%.

Do the math, since plants contribute 60% of the moisture to the air the present day high and rising CO2 has eliminated 6%-12% of the moisture being lost by dryland grasses. In dryland ecologies that is an enormous source of water. It easily explains the extended growing period of dryland grasses that has been observed but not explainable via commensurate rainfall observations.

The climate modellers keep trying to explain this living world in terms of simplified physics the biology of life keeps surprising all. The fossil CO2 we have all been pouring into our air is first and foremost the most important factor in atmospheric moisture. Four to five times more water arrives in the air as a result of plant life putting it there than arrives in the air via evaporation.

What is important on this planet are plants!

All my life I’ve thought I was doing the right thing by restoring plants, the seas and the trees. I can now do the math and show how it all works. Now that’s a cool thing to discover reading the work of a young guy at college in New Mexico. Thanks Scott!

Read the drying and dying rainforest side of this story…

More reading on Global Greening can be found here…